The present invention relates to resonators and, more particularly, to a filter comprised of a plurality of weakly-coupled micro-mechanical resonators arranged in a predetermined configuration.
Small physical structures, i.e., micro-mechanical devices, with resonant frequencies extending into the GHz spectrum may be fabricated on silicon using standard microelectronic fabrication techniques. Such devices operate surface-normal, thus permitting thousands to be fabricated on a semiconductor wafer. In addition, course lithography (i.e., 2 xcexcm line-width) provides sufficient feature and structure definition and thereby minimizes the cost of such devices. However, excitation of such structures and devices and detection of motion thereof is difficult due to their size, which may be on the order of several microns. Typical electrostatic drive and detection schemes simply are not practical due to the small size of the structures and devices.
Band-pass filters may be constructed by physically coupling a plurality of micro-mechanical resonators together using a small strip of coupling material. However, it is difficult, if not impossible, to fabricate a plurality of identical or nearly identical resonators (and the coupling material strip). Consequently, a filter thus constructed may not perform optimally.
There thus exists a need in the art for a filter that overcomes the above-described shortcomings of the prior art.
The present invention is directed to a filter constructed of a plurality of micro-mechanical resonators that are weakly coupled together. Micro-machining techniques enable the fabrication of a plurality of resonators having nearly identical frequency performance characteristics, with the difference in resonant frequency between and among the plurality of resonators being no more than approximately 1%. Any number of resonators may be coupled in virtually any configuration (e.g., circular, square, triangular, straight, etc.) to form a filter in accordance with the present invention, with the shape factor of the filter improving with the number of coupled resonators. The micro-mechanical resonators of the filter of the present invention are preferably operated in a vacuum where an individual resonator may be characterized by a Q value as high as 100,000.
The present invention is directed to a filter for detecting a predetermined frequency in a source signal and comprises a band-pass filter having a plurality of micro-mechanical resonators that are weakly coupled to each other and each having deflectable part that is caused to resonate when a signal having the predetermined frequency is directed through a first one of the plurality of resonators. The inventive filter also includes an optical source for directing an incident optical signal at the deflectable part of a second one of the plurality of resonators that is different than the first resonator. The filter further includes an optical detector for detecting an optical signal reflected by the deflectable part of the second resonator and that is indicative of the presence of the desired frequency in the source signal.
Other objects and features of the present invention will become apparent from the following detailed description, considered in conjunction with the accompanying drawing figures. It is to be understood, however, that the drawings, which are not to scale, are designed solely for the purpose of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims.